A liquid crystal display device includes a liquid crystal panel and a backlight device installed in the rear of the display panel. The backlight device includes a chassis having an opening on the liquid crystal panel side, a plurality of cold cathode tubes installed in the chassis, a reflecting sheet installed behind the reflecting sheet in the chassis, and an optical member fitted in an opening of the chassis and arranged in front of the cold cathode tubes.
Light emitted from each cold cathode tube reaches the optical member directly or after reflected by the reflecting sheet, and then travels toward the liquid crystal panel after converted into substantially flat light by the optical member.
The direction of the light reflected by the reflecting sheet can be controlled by defining the shape of the reflecting sheet, and an example of which is shown in Patent Document 1. In this example, the reflecting sheet has concave portions with a parabolic-shape cross-section. It is arranged such that concave portions surround respective cold cathode tubes. Thus, light reflected in the concave portions of the reflecting sheet travels at an angle perpendicular to the surface of the optical member. Therefore, the liquid crystal panel is illuminated with strong light.
Patent Document 1: JP-A-2004-265709
The above described art, however, still have room for improvement. After beams of light emitted from the cold cathode tubes to the rear are reflected off the concave portion of the reflecting sheet, they travel back to the tube at an angle perpendicular to the surface of the optical member. Beams of the reflected light are refracted when passing through glass tubes of the cold cathode tubes, and are most likely to travel in random directions. Therefore, light use efficiency of the above described art is not favorable.
The present technology was made in view of the foregoing circumstances, and a feature thereof is to improve light use efficiency.
The example embodiment presented herein includes a sheet-shaped optical member, a tubular light source with a substantially circular cross-section, and a reflecting member. The optical member is capable of light transmission. The tubular light source is capable of emitting light and arranged behind the optical member. The reflecting member reflects light emitted from the light source toward the optical member. The reflecting member has a concave portion for surround the tubular light source from the rear. The concave portion has an arch surface at least in an area that faces the tubular light source in a direction perpendicular to the surface of the optical member. The arch surface is formed in a concentric manner as the tubular light source.
According to this construction, a beam of light emitted from the tubular light source and reflected off the arch surface of the concave portion of the reflecting member travel in a normal direction to a surface of the tubular light source having a substantially circular cross-section. The beam of the reflected light passes the center of the tubular light source and continues toward the optical member. As a result, the beam of light emitted from the tubular light source to the rear is less likely to be refracted after passing through the surface of the tubular light source.